Sinter electrode



p 1963 L. HORN ETAL 3,102,329

SINTER ELECTRODE Original Filed Dec. 9, 1959 s Sheets-Sheet 1 INVENTOR$ ha H,

BY Mg (Am p 3, 1963 L. HORN ETAL 3,102,329

Sept. 3, 1963 L. HORN ETAL 3,102,329

SINTER ELECTRODE Original Filed Dec. 9, 1959 3 Sheets-Sheet 3 INVEN T016 m United States Patent 3,102,329 SEWER ELECTRQDE Lntz Horn, Hagen, Westphalia, and Fritz Philipp, Hagen- Haspe, Westphalia, Germany, assignors to Varta Al;- tiengesellschaft, Hagen, Westphalia, Germany Urzgmal application Dec. 9, 1955, Ser. No. 858,350. Divided and this application last. 19, W61, fies. No. 33,759

Claims priority, application Germany Dec. 1'2, 1958 Claims. (Ci. 29-l82.3)

powder such as carbonyl nickel powder (nickel powder.

which has been precipitated from carbonyl nickel vapors) during the sintering of the nickel powder. However,

sinter electrodes made in this manner can be produced by application of the nickel powder only to one face of the thin steel carrier strip.

It has also been suggested to embed stretch metal or nickel mesh in the nickel powder prior to sintering of the same. However, to thus embed reinforcing struclanes in the nickel powder is rather difficult due to the fact that the nickel powder layer which is to be sintered is very thin. Furthermore, in connection with all of the above discussed methods, the difliculty is encountered that the layer of finely sub-divided nickel powder which is to be sintered will shrink when subjected to the sintering temperatures and thereby cracks and enlarged pores will be formed in the sintered layer which adheres to the reinforcing structure. Such cracks and enlarged pores are highly disadvantageous during the subsequent impregnation of the'sintered electrode skeleton with active mass and during the formation and operation of the battery in which such electrodes are installed. in fact, imperfections. such as discussed above, might lead to destruction of the sinter electrode structure.

-It is therefore an object of the present invention to provide a sinter electrode which can be impregnated with active mass and operated without encountering the above discussed difiiculties.

it is another object of the present invention to provide a reinforced sinter electrode having a substantially even porous sintered structure of desired degree of porosity, firmly united with a reinforcing member so as to form a unitary electrode structure of the desired great mechanical strength and of very long useful life span.

Other objects and advantages of the present invention will become apparent from a further reading of the description and the appended claims.

The present invention includes a sinter electrode structure which comprises, in combination, a perforated supporting metal sheet, and a coherent porous sheet of sintere-d metal particles superposed upon one face of the perforated supporting sheet substantially completely covering the same and' extending into the perforations thereof, whereby a reinforced metallic sinter electrode structure is formed consisting of the sintered sheet and of the perforated metal sheet firmly connected to each otaer.

According to another preferred embodiment of the present invention, the sinter electrodes also comprise, in

combination, a perforated supporting metal sheet being formed with burrs at least partially surrounding the perforations and extending outwardly from one face of the perforated supporting metal sheet, and a coherent porous sheet of sintered metal particles having one face superposed upon the one face of the perforated supporting metal sheet substantially completely covering the same and extending into the perforations thereof, the burrs of the supporting sheet comprising main portions penetrating through the porous sheet of sintered metal particles and bent end portions substantially located in the plane of the other face of the coherent sintered sheet gripping the same, whereby a reinforced metallic sinter electrode structure is formed consisting of the sintered sheet and of the perforated supporting metal sheet firmly connected to each other.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a schematic elevational view, partially in cross section, of a device for producing the sinter electrode according to the present invention;

FIG. 2 is a fragmentary plane view of a portion of a perforated metallic reinforcingsheet as used in ac cordance with the present invention;

FIG. 3 is an enlarged cross-sectional view taken along 7 the lines 1'lll-H of FIG. 2;

' FIG. 4 is an elevational cross-sectional view taken along the lines lV-IV of FIG. 2;

FIG. 5 is a fragmentary cross sectional view corresponding to a View taken along lines VV of BIG. 2 and showing a portion of the perforated metal sheet of FIG. 2 after the same has been placed in contact Wtih the coherent sinter sheet, and while the porous coherent sintered mass is pressed into the perforations of the reinforcing sheet; and

FIG. 6 corresponds to the view of FIG. 5, however, after the perforated reinforcing sheet and the sintered mass have passed through the pressure rollers shown at the right-hand part of FIG. 5. v

Referring now to the drawings, and particularly to FIG. 1, the finely subdivided metal powder such as carbonyl nickel powder will be introduced through hopperl provided in its lower portion with vibrators 2 and downwardly terminating in a metal screen 3'. Upon operation of vibrators 2, the metal powder will pass through screen 3 and will flow downwardly onto an endless belt support ll. The metal powder flowing downwardly from screen 5 to endless belt suport ll is indicated by reference numeral 4. Endless belt support ll is operated by pulley drive 22. A layer 9 of metal powder is formed on endless belt support 11 and passes upon movement of the endless belt support through drying zone 5 of a sintering furnace including in addition to drying zone 5 the sintering zone 6 and coolingzone 7. Layer 9 of the metal powder passes through the entire sintering furnace and while passing through sintering zone 6, layer h will be sintered so as to form a coherent sheet. A protective gas atmosphere is maintained in sintering zone 6 and preferably also in cooling zone 7 of the sintering furnace. The sintered sheet formed of the metal powder layer 9 V and indicated by reference numeral l0 leaves the sintering furnace and is then separated from endless belt support 11 which turns downwardly about pulley 22', while the sintered sheet 10 is then supported by table 23. Endless belt support 11 is in turn supported while passing through the sintering furnace i.e. while passing through zones 5, 6

- and 7, by heat insulating ceramic plates identified by reference numeral "12.

Endless belt support 11, after turning about pulley 22. and passing scraper 16, will then pass through a magnesium oxide containing bath 14 and maintained therein below the surface of the bath by tension pulleys 13. From bath 14, the endless belt support will pass'between heating elements 13 which serve for drying the endless belt support, and from there about pulley 22 and then again underneath hopper '1.

A roll 17 of perforated metal reinforcing sheet 18, feeds the perforated metal reinforcing sheet about guide roller 22" onto table 23' so that the sintered metal layer 10 will be superposed upon perforated metal sheet 18. Perforated metal sheet 18 with the sintered metal layer thereon passes then through calibrating rollers 19, and thereby, the sintered metal powder layer is compressed and pressed partly into the perforations of metal sheet or band 18.

The thus formed electrode structurepasses then through cutter 20 and is cut by operation of cutter 20 into sinter electrode strips 21 of desired width.

Referring now to FIG. 2, the same shows a perforated metal support sheet '91 formed with perforations 92, similar to sheet :13 of FIG. 1.

FIG. 3 is a cross-sectional view taken along lines Ill- III of FIG. 2 and shows, greatly enlarged, burrs 33 which extend outwardly from sheet 31 surrounding perforations 3-2 and terminating in free end portions 34. FIG. 4 is a view similar to the view of FIG. 3 but taken along line IV-IV.

The forming of the sinter electrode according to the present invention from a sintered metal powder sheet or layer such as the sintered layer 10 shown in FIG. 1 and of a perforated reinforcing sheet such as the band 13 of FIG. 1, or the sheet 91 of FIG. 2, is illustrated in FIGS. -6.

FIG. 5 shows the sintered layer superposed upon and carried by perforated sheet 31, and-'in the right-hand portion of FIG. 5, the passing of perforated support sheets 31 and superposed sintered layer 10 through pressure rollers '19. It can be seen how the sintered layer is pressed into the perforations of support sheets 31 and how simultaneously the thickness of the sintered layer is reduced.

As illustrated in FIG. 6, the calibrating rollers may be so adjusted that the distance between the same is less than the height of burrs 33, so that not only the sintered layer 10' will be pressed into the perforations 32 of sheet 31, but also the free end portions 34 of burrs 33 will be bent as illustrated, whereby it will be achieved that the thus bent burrs will form a firm grip on the compressed sinteredv sheet 10.

Thus, according to the present invention, sinter elecneed or, in fact, should be applied to the loose layer of metal powder. Only after a sintered coherent-layer has been formed of the metal powder and has been separated from the endless belt support and contacted at one or both of its faces by perforated metal support sheets, is pressure applied, for instance, by passing the thus formed sandwiched structure between a pair of pressure rollers. The electrodes produced in this manner combine mechanical stability with flexibility. Furthermore, the thus 4.- forrned sinter electrode is of homogeneous structure, contains pores of substantially even size and is free of cracks or enlarged hollow spaces.

It has been found to be particularly advantageous to use for production of the above described electrodes a perforated metal band as reinforcing sheet, which metal band has a thickness of between 0.03 and 0.1 mm., preferably between 0.04 and 0.05 mm. 7

Furthermore, it is preferred according to the present invention, to use a rein'forcing perforated metal band having burrs or outwardly extending portions the height of which is substantially equal to the thickness of the finished sinter electrode. In this manner, a particularly stable and permanent connection between the sintered structure and the perforated support band can be achieved.

It is another advantage of the method of the present invention that, by suitably choosing the pressure with which the sintered layer is pressed against the perforated metal support band and by arranging sides and spacing of the perforations in the metal support band in accordance with the desired result, it is possible to produce sintered electrodes of any desired degree of stability and to predetermine the pore volume in the sinter electrode. In this connection, it has been found particularly advantageous to compress the lateral edge portions of the electrode band which pass through the calibrating roller about 2.5 times more strongly than the center portion between these edge portions.

Due to the very high stability of the electrode produced according to the present invention, it is also possible to further increase the surface area of the active mass by profiling the same.

'Sintering is preferably carried out at a temperature of between 600 and 1000 C., and most preferably at about 900 C. when carbonyl nickel powder, i.e. nickel powder formed of nickel carbonyl vapors, is to be sintered.

Due to the fact that in accordaucewith the preferred embodiments of the present invention, the highly porous sintered nickel layer is gripped by the burrs of the perforated metal support sheet, a firm anchoring of the sintered layer with the perforated metal support sheet is achieved and this also results in an improvement of the conductivity of the electrode so that charging and dis charging can be carried out with higher current density.

Since sintering of the nickel powder or the like takes place prior to contact between the sameand the perforated metal support sheet, thedifference in the thermal expansion coefiicients of the metal powder, on the one hand, and of the perforated support sheet will be of no significance. Thus, according to the present invention, the cracks and cavities which are formed in the sintered layer when the same is sintered on a metal support band and which are due to the. difference in the thermal expansion coeflicients between the sintered metal powder and the metallic support, will not occur according to the present invention.

As perforated metal support sheet or band, preferably a nickel plated steel foil is used.

The nickel plated steel band or foil is then perforated, however, contrary to usual practice, the burrs formed in connection with perforation of the steel foil are not removed. The width of the nicked'plated steel band is preferably, however, without limiting the present invention to the specific dimensions given herein, between about and 1000 mm. and the sinter electrode band formed thereof is subsequently cut to the desired width, usually between 4 and 200 mm.

It has been found that the thickness of the nickel plated steel foil preferably should not exceed 0.1 mm. and that it is preferred to use a perforated reinforcing sheet having a thickness. of between 0.04 and 0.05 mm.

The individual perforations may be of square shape having an edge length of between 0.1 and 0.5 mm., or

of rectangular shape wherein one pair of edges will have 'have the height of the compressed sinter layer. the height of the burrs which are obtained by form- Speed of Endless Carrier Belt Carrying Frequency of Vibrator (in Hertz) a length of between 0.1 and 0.5 and the other pair of edges a length of between 0.2 and 1.0 mm. Prefbe 0.15 and'0.25 mm. Circular perforations may have a diameter of between 0.2 and 2.5 mm. and triangular perforations a height of between 0.1 and 3 mm. The

dimensions of the perforations are so chosen that the burrs formed by perforating the metal foil will at least Thus,

ing triangular perforations having an edge length of 0.5 mm. will be between about 0.21 and 0.23 mm., and the height of burrs formed with square perforations having an edge length of 0.7 mm. will be between 0.28 and 0.31 mm.

The thickness of the sintered layer of pulvcrulent nickel or the like will depend on the speed of the endless support band which preferably will be between 0.15 and 15 mm. per second and on the oscillation frequency of the vibrators (preferably about 50 hertz), so that the thickness of the pulverulent layer can be adjusted by changing the amplitude of the vibrator; Preferably, the thickness of the pulverulent layer will be so chosen as to be about twice the desired thickness of the electrode.

The individual particles of the pulverulent nickel powder should have a sine of not exceeding microns,

- erably, the edge length of rectangular perforations will and preferably, the height of the pulverulent layer will I be between 0.3 and.1.0 mm. The pore volume after sintering will preferably be maintained at between 90 and 95% and will then be reduced by compressing the sintered layer in contact with the perforated support sheet, for instance by passing the sandwich layer through I pressure rollers, to preferably between 80 and 85%, howby thermal decomposition of nickel carbonyl vapors, it is also possible to. use other metal powders such as nickel powder which has been produced in'powder form by electrolytic methods, or a powder which has been formed of solutions of nickel salts by cementing with less noble metals.

Preferred ways of carrying out the method of the. present invention are described in three examples which follow in table form.

Table 1 Example Example Example I II III Pulverulent Nickel Through Sinter Furnace (in meter/hour).

Particge Size of Nickel Powder (in mic- 0 to 10.-. 0 to 10... O to 10.

rons

Sintering Temperature, "C 1,.000 800 900. Sintering Time 10 Min- 3 Hours; 1 Hour.

' utes. Pore Volume After Passing Through 80 82 85.

Calibrating Rollers, percent. Thickness of Calibrated Sintered Layer, 0.6 0.4 0.5

mm. Physical Appearance Cutting edges of metallic aptered layer, flexible, sintered layer firmly coherent.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various pearance, homogenous sin-.

What is claimed as new and desired to be secured by Letters Patent is:

l. A sinter electrode structure, comprising, in combination, a perforated supporting metal sheet being formed with burrs at least partially surrounding said perforations and extending outwardly from one face of said perforated supporting metal sheet; and a coherent porous sheet of sintered metal particles superposed uponsaid face of said perforated supporting metal sheet substantially completely covering the same and extending into the perforations thereof, said burrs of said supporting sheet penetrating substantially throughout the entire thickness of said porous sheet of sintered metal particles, whereby a reinforced metallic sinter electrode structure is formed consisting of said sintered sheet and of said perforated supporting metal sheet firmly connected to each other.

2. A sinter electrode structure, comprising, in combination, a perforated supporting metal sheet being formed with burrs at least partially surrounding said perforations and extending outwardly from one face of said perforated supporting metal sheet; and 1a coherent porous sheet of sintered metal particles having one face superposed upon said one face of said perforated supporting metal sheet substantially completely covering the same and extending into the perforations thereof and having an outer portion spaced from said one face, said burrs of said supporting sheet comprising portions penetrating through said porous sheet of sintered metal particles, and bent end portions in contactwith the outer portions of said coherent sintered metal sheet gripping the same, whereby a reinforced metallic sinter electrode structure is formed consisting of said sintered sheet and of said perforated supporting metal sheet firmly connected to each other.

3. A sinter electrode structure, comprising, in combina-' tion, a perforated supporting metal sheet beingformed with burrs at least partially surrounding said perforations and extending outwardly from one face of said perforated supporting metal sheet; and a coherent porous sheet of sintered meta-lpanticles having two opposite faces one of said faces being superposed upon said one face of said perforated supporting metal sheet substantially complete lycovering the latter and extending into the perforations thereof, said burrs of said supporting sheet comprising main portions penetrating through said porous sheet of v sintered metal particles and bent end portions substantially located in the plane of the other of said two opposite faces of said coherent sintered sheet gripping the same,

whereby a reinforced metallic sinter electrode structure is formed consisting of said sintered sheet and of said perforated supporting metal sheet firmly connected to each other. i 1

4. A sintered electrodestr-ucture, comprising, in combination, a perforated supporting nickel-plated steel sheet having. a thickness of between 0.03 and 0.10 mm., said sheet being formed with burrs at least partially surrounding said perforations and extending outwardly from one face of said perforated supporting metal sheet; and a coherent porous sheet of sintered metal particles superposed upon said face of said perforated supporting metal sheet substantially completely covering the same and extending into the perforations thereof, said burrs of said-supporting sheet penetrating substantially throughout "the entire thickness of said porous sheet of sintered one face superposed upon siid one face of said perforated supporting metal sheet substantially completely covering the same and extending into the perforations thereof and having an outer portion spaced from said one face, said burrs of said supporting sheet comprising main portions structure is formed consisting of said sintered sheet and of said perforated supporting metal sheet firmly connected to each other.

References Cited in UNITED STATES PATENTS Kolligs Feb. 1 9, Gaileset a1. Oct. 10, V Cemlli June 19,' McLinden July 22, Cronin Apr, 13, Carppola Dec. 9, Mourven Apr. '11, Piasqu-ale Oct. 3, Storo'hheim Dec. 12,

the file of this patent 

1. A SINTER ELECTRODE STRUCTURE, COMPRISING, IN COMBINATION, A PERFORATED SUPPORTING METAL SHEET BEING FORMED WITH BURRS AT LEAST PARTIALLY SURROUNDING SAID PERFORATIONS AND EXTENDING OUTWARDLY FROM ONE FACE OF SAID PERFORATED SUPPORTING METAL SHEET; AND A COHERENT POROUS SHEET OF SINTERED METAL PARTICLES SUPERPOSED UPON SAID FACE OF SAID PERFORATED SUPPORTING METAL SHEET SUBSTANTIALLY COMPLETELY COVERING THE SAME AND EXTENDING INTO THE PERFORATIONS THEREOF, SAID BURRS OF SAID SUPPORTING SHEET PENETRATING SUBSTANTIALLY THROUGHOUT THE ENTIRE THICKNESS OF SAID 